Cutoff valve for pistons of hydraulic self-adjusting devices

ABSTRACT

A cutoff valve for pistons of hydraulic self-adjusting devices, comprising an essentially cylindrical through element (18), attached axially to the internal end of the rod (3) of the device (1), and a cutoff element (19), also essentially cylindrical, arranged coaxially with the rod (3) on which it slides with a tight fit. The through element (18) has through holes (23) through which the liquid fluid (F) contained within the main body (2) of the device (1) can flow. The cutoff element (19) has a cutoff joint (29), which can block the holes (23) of the through element (18), and a peripheral thickening (30) provided with a sealing joint or ring (33) and a number of channels (31) through which the liquid fluid (F) can flow freely. The cutoff valve can be used in the car industry.

BACKGROUND OF THE INVENTION

The present invention relates to a cutoff valve for pistons of hydraulicself-adjusting devices, in particular for use inhydraulic-self-adjusting devices designed for the permanent, automaticadjustment of the length of control cables.

Hydraulic self-adjusting devices for the permanent, automatic adjustmentof the length of control cables are widely known and generally consistof steel cables provided with a protective sheath and attached to anactuating mechanism, such as a pedal for example, with an associatedmechanism, such as the clutch of a car for example. These self-adjustingdevices carry out adjustment independently of the initial adjustment ofthe length of the control cable, which is normally carried out when thecable is fitted by means of devices designed for the purpose thatoperate only during said initial adjustment process.

The Spanish patent P 9002014 describes a hydraulic self-adjusting devicewhich consists basically of a cylindrical main body, joined to themechanism to be actuated, and an adjustment rod, one of the ends ofwhich, the external end, is attached the control cable, whilst the otherend, the internal end, has a piston provided with a cutoff valve, saidpiston defining two semi-chambers inside the main body between which thehydraulic fluid can flow. Furthermore, said device comprises anadjustment spring and volumetric compensation means. This devicesoperates in such a way that the required increase in length of thecontrol cable as a result of the mechanical demands placed on themechanism it actuates (for example the progressive wear of the facing onthe clutch plate of a car) is provided by the increase in length of theportion of the adjustment rod which protrudes from the main body of theself-adjusting device.

One of the cutoff valves for such hydraulic self-adjusting devices whichis described by said patent P 9002014 comprises a through element, acutoff element and an opening spring which works in compression, theseelements being arranged coaxially with the adjustment rod. The purposeof the opening spring is to maintain the cutoff valve open so that theliquid fluid can flow between the two semi-chambers of the main bodywhen the adjustment rod is not being pulled by the control cable. Thecutoff valve establishes the hydraulic communication between the twosemi-chambers by means of the close fit between the cutoff element ofthe valve and the inner wall of the main body.

This cutoff valve described by the Spanish patent P 9002014 suffers fromthe drawback that it consists of a large number of components, whichincreases the cost of production of the valve as well as its assembly.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a newtype of cutoff valve which avoids the disadvantages of the prior art, inparticular a relatively large number of components of the known types ofcutoff valves.

It is another object of the present invention to provide a cutoff valvewhich has a new structure and high operational reliability.

The cutoff valve according to the invention constitutes the body of thepiston of a hydraulic self-adjusting device such as those describedabove, i.e. a hydraulic self-adjusting device which comprises thefollowing known elements: a main body which is cylindrical, elongatedand hollow and which contains a liquid fluid; an adjustment rod, one ofthe ends of which, the internal end, is fitted with said piston whilstthe other end, the external end, protrudes from the main body by avariable amount and is attached to the corresponding end of the controlcable; an adjustment spring arranged inside the main body coaxially withthe rod, said spring working constantly in compression, one of its endsresting against the end of the main body from which the rod protrudes,its other end resting against the internal end of the rod by means of atransverse support shoulder joined to said rod, such that the springtends to constantly push the rod towards the interior of the main body.

The cutoff valve according to the invention consists of a throughelement and a cutoff element. The through element is attached to theinternal end of the adjustment rod such that is forms an integral partthereof. The cutoff element is arranged coaxially with the adjustmentrod such that it can slide along it over a length determined by thedistance between the through element and the transverse support shoulderof the rod.

The through element has an essentially cylindrical shape and is providedwith a plurality of longitudinal through holes through which the liquidfluid contained within the main body can flow. The through element isalso provided with a peripheral groove which is coaxial with theadjustment rod, the size of said groove being such that is fitted with aselaing ring which, by elastic reaction, presses constantly against theinner surface of the wall of the main body, thereby preventing theliquid fluid from passing via the close fit between said wall and saidsealing joint.

The cutoff element of the valve which forms the object of the presentinvention is essentially cylindrical in shape and has a central throughhole through which the adjustment rod passes with a tight fit, the endof the cutoff element which faces the through element having a coaxialfront groove in which is fitted a cutoff joint, the size of said cutoffjoint being such that when the valve is in the closed position it blocksthe through holes of the through element, preventing the liquid fluidfrom flowing.

The cutoff valve which forms the object of the present invention ischaracterized in that the cutoff element has a peripheral thickening inwhich are arranged several longitudinal channels through which theliquid fluid contained within the main body can flow freely, saidthickening having a coaxial groove that contains a sealing joint or ringwhich, by elastic reaction, presses constantly against the inner surfaceof the wall of the main body.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate the cutoff valve for pistons ofhydraulic self-adjusting devices which forms the object of the presentinvention.

In said drawings:

FIGS. 1 and 2 are partial section views showing the valve according tothe invention fitted in a hydraulic self-adjusting device with the valvein the open and closed positions respectively.

FIG. 3 is a cross sectional view taken across the line III--III of FIG.1.

DESCRIPTION OF A PREFERRED EMBODIMENT

The cutoff valve VC for pistons of hydraulic self-adjusting devices thatforms the object of the present invention, and which is described hereinby way of example of a preferred embodiment, is attached to theself-adjusting device 1 shown in FIGS. 1 and 2, said device 1 beingdesigned the carry out the constant, automatic adjustment of the lengthof a control cable which, for greater clarity, is not shown in thedrawings. As has been said, it is understood that said control cableforms part of any mechanism in which its operation requires the constantadjustment of the length of said cable, as for example in the case ofthe control cable attached to the pedal which operates the clutch of acar. The self-adjusting device 1 shown in the drawings thereforeconstitutes only an illustrative example and may adopt any otherconfiguration which is suitable for a particular application withoutaffecting the basic concept of the invention.

The self-adjusting device 1 comprises a main body 2 which contains theliquid fluid F, an adjustment rod 3, an adjustment spring 4 and a piston5, said piston 5 defining two semi-chambers 6 and 7, front and rearrespectively, inside the main body 2.

The diagrams show that the main body 2 has an elongated, hollow,essentially cylindrical shape, at the front end A of which is an axialextension 8 that enables the device 1 to be attached to a fixed point 9,and at the rear end of which is a closing cover 10 that may comprisevolumetric compensating means which, for the same reasons as describedabove, are not shown in the drawings.

FIGS. 1 and 2 show that the front or external end 11 of the adjustmentrod 3 protrudes from the main body 2 via a through hole 12 such that itcan slide with a tight fit, said hole 12 being provided with sealingmeans 13 to prevent the leakage or escape of the liquid F to theoutside. The piston 5 is arranged at the rear or internal end 14 of therod 3, said piston comprising the cutoff valve VC which forms the objectof the present invention.

FIGS. 1 and 2 show that the adjustment spring 4 is helicoidal, has anessentially trunco-conical shape and is arranged coaxially with theadjustment rod. The spring 4 works constantly in compression, its widerdiameter resting against a step 15, via a washer 16, which defines thehole 12 in the front end A of the main body, the smaller diameter of thespring 4 resting against the transverse support shoulder 17 fixed to theinterior end 14 of the adjustment rod 3. In this way, the elasticreaction of the adjustment spring 4 tends to constantly force theprotruding portion of the adjustment rod 3 towards the interior of themain body 2.

The above description of the self-adjusting device is known and iscommonly used in self-adjusting devices designed to carry out theconstant, automatic adjustment of the length of control cables.

The diagrams show that the cutoff valve VC that forms the object of theinvention comprises a through element 18 and a cutoff element 19, bothproduced preferably by the injection of a light alloy material such asthe zamak alloys.

The through element 18 has an essentially cylindrical shape and isformed by injection onto the knurling provided for the purpose on theinternal end 14 of the adjustment rod 3. In this way, the knurling 20 istherefore inside the cavity 21 of the through element 18 such that saidthrough element 18 forms an integral part of the adjustment rod 3. Withthis arrangement, during the operation of the device 1, the throughelement 18 is prevented from changing its position relative to theadjustment rod 3, i.e. the through element 18 is prevented from rotatingabout the adjustment rod 3.

The cutoff element 19 also has an essentially cylindrical shape and isarranged coaxially with the adjustment rod 3 by means of the axial hole22, the size of said hole 22 being such that the cutoff element 19 canslide with a tight fit on said rod 3 over the portion that lies betweenthe through element 18 and the transverse support shoulder 17.

FIGS. 1 and 2 show that the through element 18 is provided with throughholes 23 through which the liquid fluid F can flow, the rear opening ofsaid holes 23 having a channel 24 designed to increase the passage crosssection of the fluid F in said portion of the hole 23. The throughelement 18 is provided with a peripheral groove 25 in which is fitted asealing joint 26 which, by elastic reaction, prevents the liquid fluid Ffrom passing via the close fit between said sealing joint 26 and theinner surface 27 of the main body 2.

The end of the cutoff element 19 which faces the through element 18 hasa front groove 28 which is coaxial with the adjustment rod 3 and whichdefines a housing in which a sealing joint 29 is firmly fitted.Laterally, the cutoff element has a peripheral thickening 30 providedwith three longitudinal channels 31, arranged at regular intervals,through which the liquid fluid F can flow freely. The peripheralthickening 30 has a coaxial groove 32 in which a sealing joint or ring33 is firmly fitted and which, by elastic reaction, presses constantlyagainst the inner surface 27 of the main body 2.

With the self-adjusting device 1 assembled according to the requirementsof each specific application, the operation of the cutoff valve VCaccording to the invention is as follows:

In FIG. 1 the cutoff valve VC is open. In this situation the liquidfluid F can flow freely between the two semi-chambers, front 6 and rear7, of the main body 2 via the longitudinal channels 31 of the cutoffelement 19 and the longitudinal through holes 23 of the through element18. The cutoff element 19 maintains its position relative to the throughelement 18 by means of the elastic reaction of its sealing joint or ring33 which, as has been said, presses constantly against the inner surface27 of the main body 2.

When the adjustment rod 3 is pulled by a force FU which is greater thanthe elastic reaction of the adjustment spring 4, said rod 3, togetherwith the through element 18 of the cutoff valve VC of the inventionwhich is joined to it, are made to slide towards the outside, the cutoffelement 19 remaining in the position it occupied before the force FC wasapplied due to the action of its sealing joint 33. As the rod 3 and thethrough element 18 move, the adjustment spring 4 is further compressedand a certain volume of liquid fluid F flows through the longitudinalchannels 31 of the cutoff element 19 and the through holes 23 of throughelement 18. The through element 18 continues to move until it meets thecutoff element 19, as shown in FIG. 2, at which point the sealing joint29 of the cutoff element 19 blocks said holes 23 in the through element18, preventing the liquid fluid F from passing through them. Thereafter,the incompressibility of the liquid fluid F inside the frontsemi-chamber 6 of the main body 2 causes the adjustment rod 3 to stopmoving inside the main body 2 at the same time that the rod 3, thethrough element 18 and the cutoff element 19 become joined together.

When the force FU applied to the adjustment rod 3 stops acting, theelastic reaction of the adjustment spring 4 forces the rod 3 towards therear end P of the main body 2, such that the cutoff element 18 joined toit separates from the cutoff element 19. When the through element 18 andcutoff element 19 separate, the sealing joint 29 of the cutoff element19 no longer blocks the through holes 23 of the through element 18 suchthat the liquid fluid F can circulate freely through them. It is duringthe opening of the cutoff valve, i.e. during the separation of thethrough element 18 and cutoff element 19, that the volumetriccompensation dynamics of the liquid fluid F contained in both the front6 and rear 7 semi-chambers, via the channels 31 of the cutoff element 19and the through holes 23 of the through element 18, overcoming theelastic reaction of the sealing joint or ring 33 of the cutoff element19, cause the cutoff element 19 to move towards the front end A of themain body 2. The amount of this displacement of the cutoff element 19 isa function of the variation in the length of the portion of theadjustment rod 3 contained within the main body 2 relative to the lengthof said portion of the rod 3 before it was pulled by the force FUapplied to its front end 11.

In this way, the cutoff valve VC that forms the object of the inventionis once again arranged to operate as explained above and, as describedin the previous paragraph, the cutoff element 19 occupies a new positionrelative to the through element 18 according to the mechanical demandsto which the adjustment rod 3 of the device 1 is subjected. Thus, apartfrom comprising a reduced number of components, giving it a highoperational reliability as well as a reduced production cost, the valveVC which forms the object of the invention provides a solution to thelimitations of some known types of cutoff valve due to the relativelyreduced volume of liquid fluid F which flows through the valve duringthe cutoff operation when it is forced by the adjustment rod.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions differing from the types described above.

While the invention has been illustrated and described as embodied in acutoff valve for pistons of hydraulic self-adjusting devices, it is notintended to be limited to the details shown, since various modificationsand structural changes may be made without departing in any way from thespirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.

I claim:
 1. A cutoff valve for a piston of a hydraulic self-adjustingdevice which includes a substantially cylindrical hollow body with aliquid fluid, an adjustment rod with an internal end provided with thepiston and an external end protruding outside of the main body, anadjustment compression spring arranged inside the main body and havingone end resting against an end of the main body from which the rodprotrudes and another end resting against an internal end of theadjustment rod through a transverse support shoulder provided on therod, the cutoff comprising an essentially cylindrical through element,an essentially cylindrical cutoff element, said through element beingattachable to the internal end of the adjustment rod and having aplurality of longitudinal through holes through which the liquid fluidcontained in the main body can flow, said cutoff element being slidableon the adjustment rod between said through element and the transversesupport shoulder, said cutoff element having an end which faces saidthrough element and is provided with a coaxial front groove; a cutoffjoint arranged in said coaxial front groove and having such a size thatwhen the valve is in a closed position it blocks said through holes ofsaid through element thus preventing the liquid fluid from flowing, saidcutoff element having a peripheral thickening with a plurality oflongitudinal channels through which the liquid fluid contained withinthe main body can flow freely, said thickening having a coaxial grooveprovided with a sealing element which presses constantly against aninner surface of the main body.
 2. A cutoff valve as defined in claim 1,wherein said sealing element in said coaxial groove of said thickeningis formed as a sealing joint.
 3. A cutoff valve as defined in claim 1,wherein said sealing element in said coaxial groove of said thickeningis formed as a sealing ring.
 4. A cutoff valve as defined in claim 1;and further comprising means for fixing said through element to theinternal end of the adjustment rod and including peripheral knurling onthe internal end, said through element being formed on said knurling byinjection.
 5. A cutoff valve as defined in claim 1, wherein said throughelement has a peripheral groove which is coaxial with the adjustment rodand having a size such that a sealing joint is fitted in said peripheralgroove and by elastic reaction presses constantly against an innersurface of the main body so as to prevent the liquid fluid from passingvia a close fit between the inner surface of the main body and saidsealing joint.
 6. A cutoff valve as defined in claim 1, wherein saidcutoff element has a central through hole so that said cutoff element isarranged coaxially with said adjustment rod, said through hole having asize such that said cutoff element is slidable on the adjusting rod witha tight fit over a length determined by a distance between said throughelement and the transverse support shoulder of the rod.
 7. A combinationof a hydraulic self-adjusting device with a cutoff valve, comprising thehydraulic self-adjusting device including a substantially cylindricaland hollow main body for containing a liquid fluid, an adjustment rodhaving an internal end provided with a piston and an external endprotruding from said main body, wherein said adjustment rod has atransverse support shoulder, an adjustment compression spring arrangedinside said main body coaxially with said rod and having one end restingagainst an end of said main body from which said rod protrudes andanother end resting against said internal end of said adjustment rodthrough said transverse support shoulder; and the cutoff valve includinga cutoff valve for the piston of a hydraulic self-adjusting device whichincludes a substantially cylindrical hollow body with a liquid fluid, anadjustment rod with an internal end provided with the piston and anexternal end protruding outside of the main body, the adjustmentcompression spring arranged inside the main body and having one endresting against an end of the main body from which the rod protrudes andanother end resting against an internal end of the adjustment rodthrough a transverse support shoulder provided on the rod, the cutoffcomprising an essentially cylindrical through element, an essentiallycylindrical cutoff element, said through element being attachable to theinternal end of the adjustment rod and having a plurality oflongitudinal through holes through which the liquid fluid contained inthe main body can flow, said cutoff element being slidable on theadjustment rod between said through element and the transverse supportshoulder, said cutoff element having an end which faces said throughelement and is provided with a coaxial front groove, a cutoff jointarranged in said coaxial front groove and having such a size that whenthe valve is in a closed position it blocks said through holes of saidthrough element thus preventing the liquid fluid from flowing, saidcutoff element having a peripheral thickening with a plurality oflongitudinal channels through which the liquid fluid contained withinthe main body can flow freely, said thickening having a coaxial grooveprovided with a sealing element which presses constantly against aninner surface of the main body.
 8. A combination as defined in claim 7,wherein said sealing element in said coaxial groove of said thickeningis formed as a sealing joint.
 9. A combination as defined in claim 7,wherein said sealing element in said coaxial groove of said thickeningis formed as a sealing ring.
 10. A combination as defined in claim 7;and further comprising means for fixing said through element to saidinternal end of said adjustment rod and including peripheral knurling onsaid internal end, said through element being formed on said knurling byinjection.
 11. A combination as defined in claim 7, wherein said throughelement has a peripheral groove which is coaxial with the adjustment rodand having a size such that a sealing joint is fitted in said peripheralgroove and by elastic reaction presses constantly against an innersurface of said main body so as to prevent the liquid fluid from passingvia a close fit between the inner surface of said main body and saidsealing joint.
 12. A combination as defined in claim 7, wherein saidcutoff element has a central through hole so that said cutoff element isarranged coaxially with said adjustment rod, said through hole having asize such that said cutoff element is slidable on said adjusting rodwith a tight fit over a length determined by a distance between saidthrough element and said transverse support shoulder of said rod.